Preheat a Traeger grill or pellet smoker to 225ºF with the lid closed. While the grill preheats, season the chuck roast with the fajita seasoning on all sides.

Smoke the seasoned chuck roast until the internal temperature reaches 160ºF to 170ºF, about 3 hours. (Slow cooker instructions in the notes section below.)

Add the thinly sliced onion to the bottom of a Dutch oven or grill pan before placing the smoked chuck roast on top. Add the ranch seasoning, beef tallow or butter, and the pickled jalapeño peppers along with some of the juice.

Increase the grill temperature to 275ºF and place the covered Dutch oven on the grill for 3-4 hours until the beef is fall apart tender. The internal temperature should be in the 205ºF range. (You can also braise in an oven since the roast won't take on any more smoke.) Take the braised chuck roast off the grill and shred the beef in the juices. If the roast is at the right temperature but a little tight, let it rest for 30-60 minutes before shredding.

For tacos, I like to increase the grill temperature to 500ºF and throw tortillas on the grill topped with queso Oaxaca or Monterey jack cheese for a few minutes to melt the cheese. Fill the cheesy tortillas with the beef and garnish with diced white onion or pickled onion, fresh cilantro, and lime wedges.